家鶏の繁殖集団における期待選抜強度と実現選抜強度

抄録

Selection differential is defined as average superiority of selected birds over the unselected population from which they were chosen. It was calculated sepa:rately for cockerel, pullet and yearling-hen breeders at different stages of reproductive cycles, as follow : (I₁) Intended or initial selection was measured as average superiority of the mean of birds selected as breeders over the mean for all birds in the unselected p, opulation from which the breeders were chosen. Modification of intended selection due to any association of the performance of each, selected bird with (I₂) the number of eggs set from it during the breeding season. (I₃) ithe number of chicks hatched from its mating, (I₄) the number of pullet progeny housed. and (I₅) the number of pullet progeny completed their records. The last one is the realized selection. Each selection differential under (I₂)-(I₅) was the weighted mean of individual or family superiority over the mean of all birds of the unselected population. Automatic selection due to association with family size was calculated as the mean of progeny minus the corresponding mean of all full-sisters' average. This is the selection automatically applied because of differences in family size.